1. Field of the Invention
The present invention relates to a housing for a gun sight system, and more particularly to a housing for mounting an improved thermal imaging system which is especially designed to fit within the U.S. Army's M1A2 Main Battle Tank and other combat vehicles with little or no alteration.
2. Description of the Related Art
The M1A2 Abrams Main Battle Tank uses a thermal imaging gun sight system to control a 120 mm main gun. The conventional sight system operates in two modes through a lens system, one mode to be used in day time and the other mode to be used at night or when the battlefield is obscured. It was found during the fighting in and around Iraq in 1991, popularly referred to as "Desert Storm", that there was a need for increased performance of the gun sight system to allow improved targeting at greater distances. With a range of 3500 yards for the main gun, it can be appreciated that the need for a high performance gun sight system is substantial.
A new three field-of-view thermal imaging gun sight system has been developed by the Hughes Aircraft Company and is the subject of co-pending patent application filed herewith, Entitled "Thermal Imaging System For A Military Vehicle," Ser. No. 08/430,791, (Attorney Docket No. PD-95 124) the teachings of which are incorporated herein by reference. The new system incorporates a high 16.times. magnification telescope with the existing 3.times. and 10.times. telescope used in the current system. The 16.times. magnification capability represents more than a 30% increase in system performance compared to the existing 10.times. telescope.
A problem has been encountered in that the new sight system is required to fit within the confines of an existing M1A2 tank. The M1A2 tank includes an exterior viewing port mounted to the tank's turret immediately above the gunner's position inside the turret. Below the external viewing port is an internal housing which extends downwardly into the crew compartment and is fixed in place. A new gun sight system is required to mount within the internal housing and within the dimensional restrictions imposed by the interior of the tank's turret. Prior attempts to meet these constraints had serious shortcomings.
Hence, there is a need in the art for an improved housing to mount the new sight system within the existing confined spaces provided. There is also a need to reduce the chance of damage from handling of the sight system. Problems have been encountered with the existing sight system when it is removed from the tank for maintenance, repair or replacement. The housing to which the system is attached requires a special jig for its support at a work bench or in the field.
There are also problems with the existing housing in relation to the ease by which a gunner is able to operate the controls of the sight system. Again, these problems are caused by the confined spaces within a crew compartment and also by the stress induced by combat.
Also, the sighting system is a very complicated and sophisticated instrument which must be carefully aligned with the tank's turret and thereby the main gun mounted to the turret. There is a need to provide for fine alignment adjustments. In addition, the importance of high optical performance and the cost of tanks and other military vehicles mandate a retrofit of existing vehicles. However, as mentioned, a practical problem facing the manufacturer of a thermal imaging system is that any new system must conform within the aperture and dimensionality constraints or "form factor" of the vehicles. This problem has been addressed by the use of a multiple field of view optical arrangement by which different sets of lens are substituted within the housing depending on the desired range or field of view.
Unfortunately, this requires the user to manually replace one set of lenses with the other and also possibly requires the manual focusing (compensation) thereof.
Accordingly, what is needed is an improved thermal imaging system that affords various powers of magnification and fields of view within conventional form factor constraints which has an automatic focus compensation.